Field of the Invention
The present invention relates generally to antimicrobial compositions and processes for using those compositions in fermentation processes. More specifically, the invention relates to the use of organic oxidizing compounds as an alternative to antibiotic agents to control bacteria in the fermentation mash of an ethanol production system.
Description of the Related Art
In ethanol production, yeast (Saccaromyces cerevisiae) is used to convert sugar into ethanol. Other microorganisms can compete with the yeast for the sugars. These microorganisms include, but are not limited to, lactic acid and acetic acid bacteria. When acid bacteria grow, they compete with the supply of sugar resulting in less sugar for ethanol production. Also, acid forming bacteria can create low pH conditions that tend to inhibit the growth of the ethanol producing yeast.
In order to control the growth of acid producing bacteria, antibiotics are added to the fermentation tanks. The antibiotics allow the yeast to kill much of the acid bacteria, but the antibiotics do not harm the yeast. The conventional method calls for the addition of 3 to 5 pounds of antibiotic, usually Virginiamycin, per 500,000 gallons of corn mash in the fermenter. The actual dose of antibiotics is determined by the level of lactic acid in the corn mash during the first 30 hours of fermentation.
Antibiotics, though generally effective, have several major disadvantages. The main disadvantage is that the antibiotics carry through the fermentation process and distillation process and end up in the distillers grains (DGs). DGs are composed of protein, oil and fiber and are what is left of the corn mash after fermentation. The DGs provide a valuable feed product but with trace antibiotics, many cattle feeders are reluctant to use DGs or must ration the DGs in the animal feed. Trace antibiotics in the DGs are thought to cause bacteria to mutate to an antibiotic resistant strain. The FDA is currently considering banning the use of antibiotics in ethanol production due to the carry over of trace amounts of antibiotics. A second disadvantage of antibiotics is that acid bacteria can become resistant over time rendering the use of antibiotics less effective and resulting in ethanol production losses.